While some people have suggested that animals use language, this is generally not accepted among linguists. Animals, including most higher primates, are known to have semantics, that is sounds that correspond to arbitrary meanings and some animals. Additional some parrots studied are known to have dialects, where the "words" they use differ among regional groups, and new members must learn them. There is also the possibility that some species, such as prairie dogs which may form simple sentences with nouns and adjectives. However, there are no species apart from humans known to use recursion, which is considered by linguists of the Chomskyan school of linguists the defining feature of human language.

According to Hockett, there are several design features possessed by human languages, but not animal languages, including the following:

Reflexivity: We can use language to talk about language, e.g. Don't use a preposition at the end of a sentence!

Displacement: We can talk about events spatially and temporally distant from us, e.g. I saw a strange guy in the pub yesterday.

Arbitrariness: There is little connection between signifier and signified. For example, the word moon is completely random; the moon does not make a 'moo' sound like a cow or otherwise exhibit features that would justify the use of moon as a sign.

Productivity (or creativity in Chomskyan linguistics): There is a limitless number of potential utterances in the language. The car ate the marshmallow-hating helicopter, for example, is a sentence that nobody has seen before, but any speaker of English can understand it.

Cultural transmission: Culture is passed on from mother to child by language acquisition. This culture is not innate, unlike animal language. Cows are biologically designed to go moo, and pigs to go oink; there is no culture transmission there.

Duality: Human language has two distinct levels, the sound and the meaning. Sounds are limited but meaning is not. We can play with the sounds in our language to produce different meanings. Consider the minimal pair made and paid. Made is broken down to the phonemes /m/, /eɪ/ and /d/, and we can swap /m/ for /p/ to produce a word with a different meaning altogether. However, animals do not have this two-level distinction. A pig may say oink, a word that means 'I'm starving', but it cannot reformulate the sounds to produce a different utterance, say, roink, replacing the glottal stop /ʔ/ at the beginning with /ɹ/. The signifier and the signified are processed on the same level, rather than two different levels.

A theory of the linguistic origins must take into account the complexity of human language. Steven Pinker argues in his book The Language Instinct that human language is like an elephant's trunk--a very complex system in which the intermediaries have been lost, but nonetheless not a hopeless problem, if we can work out the stages of language development.